scribner



(No Model.)

0,3. SGRIBNER; MULTIPLE SWITGHBOARD SYSTEM P01/I'TELEPHNEJEXGHKNGES.

UNITED STATES CHARLES ESCRIBNER, OE CHICAGO,

iLLrNois, AssIGNoR rro THE WESTERN ELECTRIC COMPANY, OF SAME PLACE.

MuLuPLE-swucHBoARo sYsT SPECIFICATION forming part of Letters'Pateint No. 51 1,464,`dated December 26, 1893.

Application tiled April 26, 1893.

To @ZZ whom, t may concern.`

Be it known that l, CHARLES E SoRIBNER, a citizen of the United States, residing at Chicago, 1n the county of Cook and State of Illi- 5 nols, have invented a certain new and usel fullmprovement in lVIultiple-Switchboard Systemsfor Telephone-Exchanges,(Case No. 325,) of which the following is a full, clear, concise, and exact description, reference being had to Io the accompanying drawing, forming a part of this specilication.

My invention relates to multiple switchboard systems of telephone exchanges. Its obgect is to provide a system of circuits such that the signal receiving annuuciator of any telephone line, while remaining permanently connected with the line-circuit,shall be inoperative or irresponsive to signalingcurrents in the circuit during the connect-ion of the line with another telephone line.

Asis well known in the art to which myinvention pertains it is a requirement of the multiple type of switchboard, in'which the annunciators of the different telephone lines are distributed upon different sections ot` the switchboard, that the individual annunciators of any two lilies which may be connected by means of the switching appliances mustbe inoperative or irresponsive to `signaling currents in their line circuits during the eX- istence ot' such connection, in order to prevent the annunciators from giving false call-indicating signals when their lines are alreadyin use upon some other section of the switchboard. Heretoforethishasbeen accomplished in different ways, one commonly employed being the provision of an auxiliary magnet adapted to prevent theactuation of.the-annunciat'or when energized, the auxiliary magnet being included in a normally open local circuit exten ding to each section of the switchboard and adapted to be closed by the act of establishing connection with the line at any section; whereby the annunciator is rendered inoperative as long as suchconnection exists.

In my invention I have aimed to dispense with local and independent circuits and with all accessory mechanism for the purpose of preventing the actuation of the annunciator. I so arrange the circuits ofthe telephone line at the central office, in combination with cer- EM FOR TELEPHONE-EXCHANGES.

` Serial No. 471,976. (Nomodel.)

tain resistance and impedence coils and the clearing-out annunciator provided in circuit with the plugs by means ot' which connection is established between lines, that during the connection of the clearing-out annunciator with the line circuit the individual or permanently connected annunciator is included in a conductor between whose terminals no difference of potential exists when a variable cur- 6o rent traverses the line circuit. The arrangement becomes, in fact, similar to' the well known Wheatstone bridge, the resistance and impedence coils and the clearing-out annunciator constituting the sidesot the bridge, and the individual annunciator being located in the bridge wire thereof. Thus in the system of my invention the individual annunciator of the telephone line is ordinarilyincluded directly in the path of the current through the 7o line circuit so as to be traversed and actuated thereby; but when connection is made with the line through the medium of the connecting plugcircuit including a clearing-out annunciator, the individual annunciator is no longer in the path of current over theline, and remains irresponsive, while the temporarily connected clearing-outannunciator receives and indicates the signal for disconnection.

In order to attain the most satisfactory results, certain proportions must be observed among the different resistances and impedence coils, as will be hereinafter fully described.

I have illustrated my invention in the accompanying drawing and will describe it in greater detail with reference thereto.

In the drawing are shown two telephone substations, designated land 2,respectively, 9o connected by line circuits with a central oice. At the central ofceeach line circuitl is connected with the usual springjacks or terminal sockets, one upon each of the two sections of multiple switchboard, and with an indi- 95 vidual 'annunciator located upon one of the switchboards. Thus the circuit of station 1 may be traced over thepline wires c c to the central station, where they are connected with t the line spring b andthe thimble b', respecttoo ively, of a springjack 'c;this springjack is assumed to be located upon a section d of a multiple switchboard. From the springjack c the circuit is continued to the spriugjack c upon the section cl of the switchboard. Upon the latter section is also located an in dividual annunciator cof ordinary construction. The side cof the line is continued from the springjacks through a resistance coil f and thence to one terminal of an annunciator e, and also through an inpedence coil g to earth. The other side a of the line circuit is connected with the remaining terminal ot the annunciator, and through a resistance coil 7L to earth.

The apparatus at the substation l is of ordinary character. It comprises a telephone set i, and a generatork ot' alternating signa-L ing current and a signal bell Z adapted to re spond to such current. The telephonie and signaling appliances are connected with the switch contacts of a switch hook m which is designed to support the telephone and to be actuated by the weight thereof to switch the telephonie and signaling `appliances alternately into connection with the line as the telephone is removed from or placed upon the hook. One terminal of the signaling generator is groundeddirectly; the other terminal is connected with a contact point of an automatic switchactuated by the rotation of the generator to connect with the line a, the switch being arranged to open the branch including the bell at the same time. The substation 2 is equipped with similar apparatus and is similarly connected byline wires ft2 a3 with springjaclrs c2 c3 upon the `dilt'erentsections d CZ', respectively, of the switchboard, and with an individual annunciator e', located upon the section CZ ot' vthe switchboard in order to be under the care of a different attendant operator.

The appliances by which the operator is enabled to switch any line into connection with any other line upon the switchboard are of the usual and well known character. The apparatus consists of a pair ot loop plugs n n' adapted for insertion into the springjacks, connected by conductors o o. When the plugs are inserted intoditterent springjacks, the line springs and the thimbles, respectively, of the springjacks are electrically connected together through the corresponding portions of the loop plugs and the conductors joining the latter together. rlwo keys 19 and p are included in the circuit of the conductor o, the switch contacts of the keys being so arranged that when the plunger of either key is depressed, it disconnects one contact piece of the corresponding plug from that of the other `plug and connects it with a grounded generator q of signaling current. A third key r is furnished for each plug circuit adapted to connect an operators telephone set s with the plug circuit when it is toperated. A clearing-out annunciator t is permanently connected in a bridge wire joining the conductors 0.o ot the plug circuit; it is constructed to beA of considerable impedator.

ence, in order that it may not permit any appreciable shunting of the rapidly alternating telephonie currents through it from the line conductors. One pole ot a battery u is connected with the conductor o which joins the sleeve contacts of the loop plugs, an impedence coil c being preferably included in the circuit to prevent the escape of telephonie current to earth through the battery. The battery u is provided for testing purposes; its operation will be referred to later. A portion of a similar plug circuit is shown at the section d of the switchboard, the plug n2 being in the position of testing the springjaek c' at that board to determine whether the line is in use or not.

' In the drawings, the snbstations l and 2 ,are shown connected together through the `medium of the plug circuit at the section d ot the switchboard, the station 12 being assumed to have initiated the connection. In the process of thus obtaining such connection between stations 2 and l, the subscriber `at station 2 first rotates his signaling generator la, thus sendinga signalingcurrent over the line a2 to the central station, where lit Vtinds circuit through the resistance coilf' to one terminal of the annunciator e; therefrom to earth it has two paths--one through the individual annunciator e and thetresistence coil h', and the other through the impedence coil g. rlhe high self-induction of the latter coil prevents any considerableportion of the rapidly alternating currenttraversing it, whereby the current is directed `through the annunciator and the resistance coil 71. to earth. The annunciatorbeingthus operated, attracts the attention of the `operator at section (l of theswitchboard,whereon it islocated. The operator insertsone .pl-ug n of a pair into the springjack cgantlidepresses the plunger of her listening keyr, connecting her telephone sets in circuitwith the apparatus lat the substation. NVhen .the subscriber has removed` his` telephone from the hook, the circuits are in condition to permit hirn to give his order `orally vto `the -operrlhe `operator having th ns learned that connection with station 1 is desired, makes a test to determine whether thatline isalready in use or notupon the `other section` of the multiple switchboard. This sheldoesbyiapplying to the thimble or test `ring .19 of` the` sprin gj ack c uponher board the tip of theplug n, as the plug n2 is shown applied .tothe test ring ot' springjack c upon board d. lftheline tested is in use, a battery u isconnectedlwith the thimbles or test rings ot' the line through the medium of theconductor o andthe sleeve of the plug by means of which such connection already exists, the sleevebeingin ,contact with the thimble of the springjack intowhich it is inserted, whereby the test4 rings` are` electritied to a diterence of `potential from .the earth, and a current will flow from the thimble through the tip of. theplug to the conductor o and thence through the listening key fr and IOO one half of the coil of the telephone receiver s to earth, producing a click in the telephone at each application ot the testing plug to the springjack. It the line were not'in use, obviously no sound would be produced in the telephone since no source ot' current would be connected with the line. Finding the line to station l not in use, the operator inserts the plug n fully into the springjack c', completing a continuous metallic circuit between the two substations, including the line wires a a to station l, the conductors o 0 of the plug circuit, and the line wires a? a3 extending to substation 2. The operator then depresses the plunger of calling key p, wherebythe grounded calling generator q is connected with the side a ot' the liner circuit, and sends current over the line to substation 1, where it finds circuit through the signaling bellZto the line a', returning over that line wire to the central station and through the resistance coil h to earth. Theannunciator e is not operated, since such a proportion exists between the effective resistances of the impedence coil g, the resistancecoil h, the resistance coil f, and the circuit through the linea, the signaling bell Z and .the return line d', that no difference of potential exists between the terminals of the annunciator e, which thus re`- ceives no current. The signaling bell Z is, however, operated and calls the attention of the subscriber at station 1. Vhen the sub-l scribers have completed their conversation, one of them-for example the subscriber at station l-may again rotate his signaling generator k to send the signal for disconnection of the lines. The signaling current thus sent finds circuit over the line a as before to springjack c, where it divides, a small portion passing through the resistance coilfand the im` pedence coil g, while a larger portion passes from the line spring b of the springjack to the tip of the plug and thence to the conductor 0 ot' the plug circuit and thence through the clearing-out annunciator t to the conductor o', thence returning to the sleeve of plug n and to line a', from which it finds circuit through the resistance coil h to earth. The annunciator e is still Anot operated by this signaling current since no potential exists between its terminals. In this instance, one side of the parallelogram, of which the annunciator e is the bridge wire, is formed by the resistance coil f and the impedence coil g, while the other side of the parallelogram is formed by the conductors o o including the clearing-out annunciator t, and the resistance coil h.

Having thus described my invention, I claim as new and desire to secure by Letters Patentl. The combination in atelephone signaling circuit, of two independent branches'of'the 'open branch through an auxiliary signaling device, resistances in the different branches on each side of the terminals of the bridge wire containing the annunciator excepting 'that section of the circuit which contains the auxiliary signaling device, and a source of electric current connected with the signaling circuit,the different resistances being so adjusted with respect to each other and to the effective resistances of the auxiliary signaling device that no dierence of potential exists between the terminals ot' the annunciator, whereby the annunciator remains unoperated while the auxiliary signaling device responds, substantially as described.

2. The combination with the signaling circuit of a telephone line including a source of electric current, of two branches, one branch being normally open, a signaling annunciator in a bridge wire between the two branches, means for closing the normally open branch through a resistance when connection is vof each arranged to constitute two sides of a Wheatstone bridge or parallelogram,one of the sides being normally open, a signal re' ceiving annunciator yin the bridge wire of the parallelograin, resistances in the normally closedsides of the parallogram, means for closing the normally open side through a I signal bell and a clearing-out annunciator alternately, and means for connecting a source of signaling current in the circuit external to the parallelogram, the different resistances being so adjusted with relation to each other and to the effective resistances of the clearin g-out annunciator or bell that no diterence of potential exists between the terminals of the individual annunciator when the normally open side is closed, whereby signaling current may be caused -to operate either the clearing-out annunciator or the signal bell Without affecting the individual annunciator, or to operate the latter annunciator only.

4. The combination with a telephone signaling circuit extending from a substation to a central station, of a resistance coil in the main circuit, a resistance coil in one of vthe parallel branches, an individual annunciator and another resistance coil in the other parallel branch, and a source of signaling current included in the circuit at the substation,

whereby the annunciator is operated, sub-i` stantially as described.

5. The combination with a signaling circuit,

of a telephone line extending from a substation to a central station and divided into two parallel branches `at the central oioe, `one branch including two resistance coils, the other branch includingn a clearing-out annunciatorand `a resistance coil, an individual annunciator connected ina bridge from the point between the resistance ooilson one branch to a point between tlievclearing-out annunciator and the resistance coil on the other branch, and a source of signaling current in the circuit at the substation, the effective resistanoes of the different coils being so adjusted that no diiierence of potential exists between the terminals of the individual annunciator, subl stantially as described.

6. The combination with a signaling circuit extending in two parallel branches from a substation t'o a centralstation, of two resistance coils `included in `one ot' said branches, la signal bell Landa `resistance coil included ,in the other ofsaid branches, an individual annunciator connected in abridge wire from apoint between thetwo resistancecoilsof one branch n being grounded at the central ofticeNof two resistance coils in one `branchbot'4 lineand a single resistance coil in the other branch, an individual annunciator connected 1n a resistance coils of oneside of the line to a `point between the resistaneecoil of `the other side and the springjack, a signal bell `normally bridged between the two sides `ot' the circuit atthe substation, a grounded `generator of signaling currentadapted, whennperated, to disconnect the `bell from thesideof the line containing the two resistance coils and to connect the` generator armatnre thereto, a loop plug adapted foi-insertion into the springjack at the substationa clearing-ont annunciator normally included between the contacts of the said plu`ga key adapktemwhen operated, ,to disconnect the clearing-outlannunciator and `to connectone poleof a gronnd- 1ed generator to `the side of` the line containl ingV the two resistance coils,nwherebysignal `ing currentinay be `sent from theQsnbstatln `to operate the clearing-out anuunciator7 brit .not the ndividnal annunciator thereat, and

signals inay `be sent f roin `the,central station to the substation kto ,operate the signal bell thereat without operating the l1,ndiyidual,an-

nnunciator, substantially fas described.

In witness whereof I hereunto snbscrlbeniy name this 22dday oflylarch, A. D. 1893.

CHARLES E. SGRIBNER. Witnesses:

ELLA EDLER, LUCILE RUSSELL.

l40 bridge wire from the `point 4between `the two 

